A method for building a 3D crust-mantle velocity reference model: A case study of the central South China Block

Crust-mantle velocity structures,which provide an important basis for research on deep structures and dynamic mechanisms,are primarily determined using seismic tomography.A high-quality and fine-scale velocity reference model can provide an effective initial model and constraints for seismic tomography.However,existing methods for building a crust-mantle velocity reference model suffer some shortcomings,such as the lack of fine-scale building of the surface model and the partial distortion of the crust-mantle model caused by vertical global correction.To overcome these shortcomings,this study proposed an improved method for building a 3D crust-mantle velocity reference model.Firstly,the optimal Moho and sedimentary basement models were selected and constructed.Then,these boundary models were used to constrain and adjust the crust and upper mantle models vertically,including the linear correction and weighted fusion through partial compression and stretching.As a result,a crust-mantle medium model was established.Subsequently,the surface model was built in combination with prior geological data.Finally,these models were combined to construct a 3D crust-mantle velocity reference model.Using this method,this study built a 3D crust-mantle S-wave velocity reference model for the central South China Block by collecting previous crust-mantle structure models and geological data of the block.The comparative analysis shows that the model built in this study enjoys higher resolution and more accurate regional Moho,thus verifying the effectiveness of the method.This study provides a reliable 3D velocity reference model for the central South China Block.